The Verizon Wireless brick shop was trying hard to sell me a >$20 car charger. I steadfastly refused, because I already have a couple of USB car charger from a bluetooth headset and my previous smartphone. Besides, Verizon accessories are overpriced. To my dismay, neither of my car chargers is able to charge my Droid 4. The only reason I can think of is their output. One of the has an output of 500mA, and the other 750 mA, while the wall charger that came with my Droid 4 has an output of 850mA. Could this be really the reason? Does Droid 4 require a car charger of strictly 850mA or more? In the past, my other phones and mobile devices were easily charged through these car chargers even though their native wall chargers had higher output.